This invention relates to inflation indicators for cuffed tubes.
Medico-surgical tubes that are required to be inserted and sealed in a body passage or cavity are commonly provided with an inflatable cuff encircling the tube. The cuff is inflated via an inflation lumen to seal the tube with the body passage or cavity. In order to provide an indication of whether or not the cuff is inflated, the inflation line can support an inflation indicator in the form of a flexible envelope the interior of which communicates with the inflation line and hence with the interior of the cuff. Inflation of the cuff causes a corresponding inflation of the envelope which is readily apparent to the clinician.
The cuff on the tube is usually inflated by means of an air-filled syringe the nose of which is coupled to a coupling on the machine end of the inflation line. When it is necessary to remove the tube, the cuff is deflated in a similar way by means of a syringe, the plunger of which is withdrawn to suck air from the cuff.
One problem with this, is that the fall in pressure caused by withdrawing the plunger can cause the wall of the envelope to collapse together and seal off the gas passage to the cuff. This can be a particular disadvantage in an emergency where it may be necessary to remove the tube quickly. There is also a tendency for the inflation indicating envelope to seal off if it is bent or folded across the gas passage through it.